How to Interpret Hose, Tube & Fittings "Dash Sizes"

People that are new to the hydraulic and pneumatic industries often ask: What is a dash size? Simply put, a dash size refers to a diameter of a hose, tube or fitting in 1/16" increments.

For example, if you see the following part number:

387TC-6

You know that 387TC is one of the series numbers for GlobalCore hose, but what does “-6” mean?

Each dash size corresponds to a progressively larger diameter, measured in sixteenths of an inch. “-1” is 1/16, “-2” is 2/16, and so on. In this case, -6 hose would indicate a hose with an inside diameter of 6/16”, or 3/8".

In another example, a -10 tube would indicate a tube with an outside diameter of 10/16", or 5/8".

Fittings are a little different and slightly more complex. In the part number 10343-8-6, for example, -6 is the hose size and -8 is the size of the fitting end connection.

Did you notice that for hose part numbers, we talked about inside diameter, and for tube part numbers, we referred to an outside diameter? This is not an accident. Hoses are measured by inside diameter, and tubes are measured by outside diameter, which is how they are differentiated from each other. Most people think about hoses as being flexible and tubes as being rigid, but in fact, there are some very rigid hoses, and some very flexible tubes. For example, nylon tubing is very flexible, and flexible metal hoses are (relatively) very rigid.

So remember: dash size is the size of hose, tube or fittings expressed in sixteenths of an inch, hoses are measured by inside diameter, and tubes are measured in outside diameter.

That's all there is to it!

 

Hose Vs Tube Diameter

HOSE SIZE IS DETERMINED BY ITS INSIDE DIAMETER (A)

TUBE IS DETERMINED BY ITS OUTSIDE DIAMETER (B)


HOSE I.D (Inches)    

  All EXCEPT Transportation

& Refrigerant Hoses

Transportation

& Refrigerant Hoses 

 Dash No. Inches  Millimeters  Inches  Millimeters
 -3 3/16 5  - -
 -4 1/4 6,3 3/16 5
 -5 5/16 8 1/4 6,3
 -6 3/8 10 5/16 8
 -8 1/2 12,5 13/32 10
 -10 5/8 16 1/2 12,5
-12 3/4 19 5/8 16
-16 1 25 7/8 22
-20 1-1/4 31,5 1-1/8 29
-24 1-1/2 38 1-3/8 35
-32 2 51 1-13/16 46
-40 2-1/2 63 2-3/8 60
-48 - - 3 76

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